Is there any downside to having more return runs than are actual needed to support the outlet(heat\AC) runs. I have a 2 stage , variable speed furnance.

11-25-2005, 05:41 PM

dash

Only if it decreased the overall system static drastically,which I'm sure is not the case.

If they are oversized,in a non-uniform manor,some may "pull" too much air from one room or another.

Why do you ask??

11-25-2005, 05:52 PM

geob

Why do you ask??

When I had my furnance replaced the contractor told me that I had more than required. I asked if he should remove some so as to optimize the system. He said that's not required. I don't know if this is actually the case ... or .... he was just attempting to lessen the amount of work he had to do.

11-25-2005, 06:13 PM

Irishmist

If this is an area that you are going to worry about, then you need to have a professional come in and evaluate your complete air distribution system. Whether or not it was done at the time of this most recent installation is not so much the issue as to whether or not you're going to lose sleep over it. I can tell you that the majority of return problems are the result of too little return air as opposed to too much. But, again, if in doubt, call in a professional. p.s. if you were satisfied with your furnace installation, then this person is the best place to start.

11-25-2005, 07:01 PM

RoBoTeq

Other then not having a required static at the unit, there is basically no such thing as too much return.

The return air portion of an HVAC ducting system does not "pull" or "suck" air...it allows the higher pressure of air introduced into an area to "return" to the units blower.

HVAC systems do not have negative pressure blowers. These blowers do create a negative pressure within the direct area of the blower, but it is not like a vacuum cleaner that actually "sucks" or "pulls" air to the blower.

11-25-2005, 09:48 PM

dash

Return air is moved based on the pressure differential of the negative pressure in the return duct ,and the neutral or near neutral pressure of the air in the room.The supply air doesn't "push/move" it back to the blower.

It takes the "path of least resistance" and can "pull/move" air from rooms that it wasn't intended to,if return duct/grille is oversized in an area.

Not saying that this is the case here,just answering the OP's question of what can happen.Hopefully s/he will "learn' something!!LOL

It really does work like a vacuum cleaner,think about supply air that leaks to an attic or has no return path back.In both cases a return ,with no duct leakage ,to create negative pressure on all or part of the home,'Pulling" air in to the home from outside the envelope,basically pulling or sucking,though we often call it infiltration.

A good NCI class could clear this up for those who are confused,IMHO.

[Edited by dash on 11-25-2005 at 08:53 PM]

11-25-2005, 09:59 PM

trane

Quote:

Originally posted by RoBoTeq Other then not having a required static at the unit, there is basically no such thing as too much return.

The return air portion of an HVAC ducting system does not "pull" or "suck" air...it allows the higher pressure of air introduced into an area to "return" to the units blower.

HVAC systems do not have negative pressure blowers. These blowers do create a negative pressure within the direct area of the blower, but it is not like a vacuum cleaner that actually "sucks" or "pulls" air to the blower.

The only thing that makes sense to me is the first sentence. Maybe I'm lost but please explain the rest of your post or at least make some changes.

11-25-2005, 09:59 PM

dash

Quote:

Originally posted by RoBoTeq Other then not having a required static at the unit, there is basically no such thing as too much return.

The return air portion of an HVAC ducting system does not "pull" or "suck" air...it allows the higher pressure of air introduced into an area to "return" to the units blower.

HVAC systems do not have negative pressure blowers. These blowers do create a negative pressure within the direct area of the blower, but it is not like a vacuum cleaner that actually "sucks" or "pulls" air to the blower.

It a "low" pressure vacuum cleaner ,and the return pulls or or sucks air back,but like a vacuum cleaner it's really the pressure differential,that moves the air.True for supply as well,it's the PD.

11-25-2005, 10:00 PM

trane

Dash, you edited while I was typing. I was going to let him explain his thoughts first.

11-25-2005, 10:03 PM

dash

Quote:

Originally posted by trane Dash, you edited while I was typing. I was going to let him explain his thoughts first.

As tempting as it is I didn't want to bait him!!I likely regret that.LOL

11-25-2005, 11:45 PM

RoBoTeq

Think what you want fellows; HVAC blowers are not designed to pull air. Air, as is noted, will follow the path of least resistance and that is from a higher pressure area due to air being pushed into that area to the low pressure area of the blower as long as there is a pathway for it to "return" by.

We have gone through this before and the wrong use of terminology by dash complicated the subject then as it surely will again.

No...I will not get into this again. If dash wants to play mr. air expert, what the hell? The main point here is that the OP does not have to be concerned with having too much return path back to the blower.

11-25-2005, 11:49 PM

dash

Can you explain why the return can create negative pressure in the home causing infiltration,pulling air into the home??

No ,I didn't think so.

Or is it being pushed into the home from a supply air leak in the neighbors home??LOL

Think about it,if all the supply went to the outside of the home,what would happen to the interior of the home?And what would happen if you opened the windows,would it "pull" air in??YOU BET IT WOULD!!

Since you brought up "you guys" and what they think ,I hope they'll tell you what they think ,for a change.